Singer R, Bruchis S, Barnet M, Sagiv M, Kaufman H, Servadio C
Experientia. 1985 Jan 15;41(1):64-5. doi: 10.1007/BF02005876.
beta-Endorphin was estimated in normozoospermic, oligozoospermic and azoospermic human semen. The mean amount in normozoospermic specimens was 278.6 +/- 43.6 (SE) pg/ml while in the others only 191.1 +/- 25 pg/ml. Both values are significantly higher than those present in the blood.